GSTM1 and neoplasm: Figures 6B–E illustrate the concentration images of deoxyhemoglobin (Hb), oxyhemoglobin (HbO2), total hemoglobin (HbT), and oxygen saturation (StO2). The averaged tumor to background (T/B) contrast is calculated to be 3.09× for Hb, 2.13× for HbO2, 2.46× for HbT, and 0.87× for StO2. David et al. have found that increases in HbT and μs′ contrast showed correspondence with similar high-FDG regions in the PET images, which demonstrates that DOT is indeed sensitive to the local metabolism and may provide information complementary to PET (38).